Metallic TiN-mediated interface to boost charge transfer of bismuth vanadate toward enhanced photoelectrochemical water oxidation

Surface modification of cocatalysts is one of the most efficient strategies to improve the surface charge transfer of bismuth vanadate (BVO) photoanodes. However, the interfacial recombination between BVO semiconductors and cocatalysts is seriously undervalued. Herein, metallic titanium nitride (TiN) nanoparticles are decorated on the surface of BVO to tune the carrier dynamics at BVO/cocatalysts interface. The enlarged band bending at the near-surface of the BVO semiconductor enables significantly promoted interfacial charge transfer and separation, resulting in a much higher charge separation efficiency (83.7 %) than that of the untreated BVO photoanode (67.8 %). Subsequently, the deposition of CoFe-based oxygen evolution catalyst (CoFe-OEC) raises the charge injection efficiency of TiN/BVO from 38 % to 81 % by accelerating water oxidation reaction kinetics. Stemming from the fast charge transfer and separation at semiconductor/cocatalyst/electrolyte interface, a prominent photo-current density of 5.0 mA cm⁻² along with outstanding PEC stability can be achieved by the hybrid CoFe-OEC/TiN/BVO photoanode. This work will pave a new design avenue to enhance the carrier dynamics in semiconductor/cocatalyst system for efficient PEC water oxidation.